In the transmission of a video signal, a video encoder at a transmitter terminal receives input video data comprising a sequence of “raw” video frames to be encoded, each representing an image at a respective moment in time. The encoder encodes each input frame into an encoded frame (e.g. either as an intra frame or as an inter frame). The purpose of the encoding is to compress the video data so as to incur fewer bits when transmitted over a transmission medium or stored on a storage medium.
Each frame of video data may be encoded into one or more spatial units for respective image regions of the frame. When the video data has been encoded and transmitted to a receiver terminal, the receiver terminal decodes the spatial units for each of the image regions of the frames to thereby recover data values (e.g. luminance and chrominance values according to the YUV colour space scheme) representing the image regions. In this way the receiver terminal can recover the frames of the video signal. The recovered frames may be stored at the receiver terminal, transmitted to another terminal or output from the receiver terminal, e.g. to a user of the receiver terminal using a display of the receiver terminal.
In the transmission of a video signal, there is a trade off between the quality of the video signal that can be recovered at the receiver terminal (e.g. the resolution, frame rate and error rate of the video signal) and the amount of data that needs to be transmitted.